We really encourage welcoming new members. The entire feel of our forum depends on how warm, friendly, and approachable our members (and mods, admins, etc) are. So allow us to lead by example.
And nothing is better than a good efficient way to get things done.
So here's a quick tip to make it easy to welcome the new members, and see who you have welcomed and who you have yet to welcome aboard.

Go down the list, each thread you posted on will have a checkmark that looks like this:

See where they appear:

Those threads that don't have the checkmark mean that you have not posted there.
The pic is my actual account, I took a snapshot while doing it a few minutes ago just to show you guys and gals how I do it.

This is what you do:
Open each thread that does not have the checkmark in a new tab.
Hint: to open a link in a new tab, hold the Ctrl key when clicking the link.
So now that we have all the threads that we need to post in opened, each in a separate tab, we can paste in our favorite welcome message of the day.
The page down key on your keyboard is your friend.
As is Ctrl+V (paste) so you can easily paste your message and then move on to the next thread. To close a tab, Ctrl+W is your other friend, and the next tab in your list (from when you opened them all in new tabs ) will appear.